Wearing gloves, wash the chiles and remove the stems. I leave the seeds and ribs in for maximum hotness. If you want less heat, remove the ribs and seeds and use less spicy peppers, like cayennes.
Put everything into a non-aluminum pot (aluminum or copper will react to the acid and make it taste terrible and metallic). Bring to a boil, then turn down to a simmer.
Cook for about 20 minutes, stirring a few times, until everything is tender. Let it cool.
Put in a blender and blend until super-smooth.
Pour into a freshly washed glass bottle and refrigerate. Lasts about six months.